Key Points
- The MOSFET is a drift/majority carrier surface device.
- Carriers are attracted or repelled from the surface by
a gate potential
- At a threshold voltage the surface is inverted and for
example a n-type substrate becomes p at the surface.
- A lateral electric field between drain/source
establishes a current that is controlled by the surface density of
carriers -- which is determined by the gate potential
- Pinchoff at the drain end of the gate makes the
drain-source current independent of the drain-source voltage in
saturation
Questions
- Draw the structure of a mosfet and explain it's
operation.
- Is the mosfet a majority carrier device? Why?
- Is the primary current due to drift or diffusion?
- Is this a linear or non-linear device?
- Could a polymer be used to make a FET device? Draw the structure. What would be the differences between it and a Si based device.